[snovv_crash]

Randomly choose 3 big paragraphs in the entire ebook to add an extra newline in the middle of at the end of a random sentence. This would be my choice if I had to do some kind of invisible watermarking, at least.

[hdjjhhvvhga]

This is one of the many things that could be trivially detected and fixed when you have multiple watermarked copies of the same file.